4.3 Carbon cycle Flashcards
What is the carbon cycle?
A biogeochemical cycle where carbon is exchanged between the different spheres of the earth
How many spheres of earth are there?
Four
What are the four spheres of the earth?
Atmosphere
Lithosphere
Hydrosphere
Biosphere
What are the four ways carbon is exchanged?
Atmospheric gases
Oceanic carbonates
Organic materials
Non-living remains
How is carbon exchanged as atmospheric gases?
Mainly as carbon dioxide and methane
How is carbon exchanged as oceanic carbonate?
Bicarbonates dissolved in the water and calcium carbonate in coral and shells
How is carbon exchanged as organic materials?
Carbohydrates
Lipids and proteins found in all living things
How is carbon exchanged as non-living remains?
Detritus and fossil fuels
What facilitates the cycling of carbon between the different forma?
Different processes
How do autotrophs convert inorganic carbon dioxide into organic compounds?
Via photosynthesis
What do organic compounds include?
Carbohydrates, lipids and proteins required by the organism for survival
Why should levels of carbon dioxide within the organism should always be low?
Since autotrophs use carbon dioxide for photosynthesis
Where should carbon dioxide concentrations be higher?
In the atmosphere or water
What does the concentration gradient between the autotrophic organism and the outside ensure?
That carbon dioxide will passively diffuse into the autotrophic organism as required
In terrestrial plants where does diffusion occur?
At stomata
In aquatic producers, where does carbon dioxide diffuse?
Directly into the autotroph
What can heterotrophs not synthesise?
Their own organic molecules
How do heterotrophs obtain carbon compounds?
Feeding
What do all organisms produce to power metabolic processes?
Chemical energy (ATP)
How do organisms produce ATP?
Cell respiration
What does cell respiration involve?
The breakdown of organic molecules and produces carbon dioxide as a by product
What does the build up of CO2 in respiring tissue create and what does that allow?
A concentration gradient allowing it to be removed by passive diffusion
In autotrophs, what does may balance the uptake of CO2 by photosynthesis?
The production of CO2 by respiration
What is the compensation point?
Where the net carbon dioxide assimilation is zero
What is the amount of carbon dioxide in the environment determined by?
Cell respiration and photosynthesis
What happens if there is more net photosynthesis than cell respiration in the biosphere?
Atmospheric carbon dioxide levels should drop
What happens is there is more net cell respiration than overall photosynthesis?
Atmospheric carbon dioxide levels should increase
What does carbon dioxide dissolve in water turn into?
Carbonic acid
What happens when carbonic acid dissociatess?
Hydrogen carbonate ions are formed
Why does pH change when CO2 is dissolved in water?
the conversion of carbonic acid to hydrogen carbonate ions releases hydrogen ion
What do autotrophs absorb to produce organic compounds?
Carbon dioxide and hydrogen carbonate
What happens when hydrogen carbonate ions come into contact with the rocks and sediment on the ocean floor?
They acquire metal ions
What happens when hydrogen carbonate ions acquire metal ions?
The formation of calcium carbonate and the subsequent development of limestone
What may living animals do to form calcium carbonate?
Combine hydrogen carbonate ions with calcium
What does the calcium carbonate form?
The exoskeleton of coral and the main component of mollusca shells
What happens when the organism dies and settles to the sea floor?
The hard components become fossilised in the limestone
What are the five steps of the calcium carbonate formation in oceans?
Atmospheric/ aqueous CO2
Carbonic acid
Bicarbonate
Carbonate
Calcium carbonate
What are methanogens?
Archaean microorganisms that produce methane as a metabolic by product in anaerobic conditions
What are the three anaerobic conditions where methanogens can be found?
Wetlands
Marine sediments
Digestive tract of ruminant animals
How do methanogens produce methane?
The by product of anaerobic digestion principally acetic acid and carbon dioxide
Where does methane accumulate?
Under the ground or diffuse into the atmosphere
What happens when organic method is buried in anoxic conditions?
Deposits of methane may form underground
What is leading to an increase in the levels of methane being released into the atmosphere?
Rising numbers of domesticated cattle
How long does methane last when it is released into the atmosphere?
12 years
Why are methane levels in the atmosphere not very large despite large quantities being produced?
Because methane is naturally oxidised to form carbon dioxide and water
What will saprotrophic bacteria and fungi do to dead organisms?
Decompose them and return nutrients to the soil for cycling
Why may some waterlogged regions possess anaerobic conditions?
As they may lack oxygenated air spaces within the soil
What does the decomposition process require?
Oxygen
What does anaerobic respiration in anaerobic waterlogged regions produce?
Organic acids causing acidic conditions
Why is decomposition prevented in anaerobic/acidic conditions?
Saprotrophic bacteria and fungi cannot function effectively
Where and why does peat form?
Since the organic matter in waterlogged soils is not fully decomposed, carbon rich molecules remain in the soil and form peat
What happens when deposits of peat are compressed under sediments?
Heat and pressure force out impurities and remove moisture
What does the peat that has moisture and impurities removed have?
High carbon concentrations
What does the remaining material with a high carbon concentration undergo?
A chemical transformation to produce coal
What is oil and natural gas the result of?
The decay of marine organisms on the ocean floor
What does sediments that are deposited on top of the organic matter create?
Anoxic conditions that prevent decomposition
In oil/ natural gas formation, what happens as a result of the burial and compaction?
The organic material becomes heated and hydrocarbons form
What does the hydrocarbons form?
Oil and gas
Where are oil and gas forced out of?
Source rock and accumulates in porous rocks
Why are fossil fuels a non renewable energy source?
Because their formation takes place over millions of years
What happens when organic compounds rich in hydrocarbons are heated in the presence of oxygen?
They undergo an exergonic combustion reaction
What is released as by products when hydrocarbons are heated in the presence of oxygen?
Carbon dioxide and water
What are two combustion sources?
Fossil fuels and biomass
What can organic compounds become rich in when compacted underground for millions of years?
Hydrocarbons
What results in fossil fuels?
Heat and pressure over time triggers a chemical transformation
What is an alternative to relying on fuels produced by geological processes?
To manufacture fuels from biological processes
What do living organisms produce as part of their total biomass?
Hydrocarbons
What can happen to the hydrocarbons produced as part of a biomass?
They can extracted and purified to produce an alternative fuel source
How can biomass energy be renewable?
If new raw materials are provided and waste products are removed
What do carbon fluxes describe?
The rate of exchange of carbon between various carbon sinks
What are the four main carbon sinks?
Lithosphere
Hydrosphere
Atmosphere
Biosphere
What are the six processes the rate of carbon exchanged between sinks depends on?
Photosynthesis
Respiration
Decomposition
Gaseous dissolution
Lithification
Combustion
How does photosynthesis affect the rate of carbon being exchanged between sinks?
Removes carbon dioxide from the atmosphere and fixes it in producers as organic compounds
How does respiration affect the rate of carbon being exchanged between sinks?
Releases carbon dioxide into the atmosphere when organic compounds are digested in living organisms
How does decomposition affect the rate of carbon being exchanged between sinks?
Releases carbon products into the air or sediment when organic matter is recycled after death of an organism
How does gaseous dissolution affect the rate of carbon being exchanged between sinks?
The exchange of carbon gases between the ocean and atmosphere
How does lithification affect the rate of carbon being exchanged between sinks?
The compaction of carbon-containing sediments into fossils and rocks within the earths crust
How does combustion affect the rate of carbon being exchanged between sinks?
Releases carbon gases when organic hydrocarbons are burned as a fuel source
Are carbon sinks/fluxes measured or estimated?
Estimated
How are global carbon fluxes measured?
In gigatonnes
Why do estimates of carbon fluxes have large uncertainties?
As they are large and based on measurements of many different sources
What are the three main causes of carbon flux changes?
Climate conditions
Natural events
Human activity
When will rates of photosynthesis be higher and why?
In summer seasons as there is more direct sunlight and longer days
What do oceanic temperatures determine about carbon?
How much is stored as dissolved CO2 or as hydrogen bicarbonate ions
How does El nino and La nina affect carbon fluxes?
They change the rate of carbon flux between ocean and atmosphere
How does the melting of polar ice caps affect carbon fluxes?
It results in the decomposition of frozen detritus
How do forest fires affect carbon fluxes?
They release high levels of carbon dioxide when plants burn and the loss of trees also reduces photosynthetic carbon uptake
How can volcanic eruptions affect carbon fluxes?
They release carbon compounds from the earths crust into the atmosphere
How does deforestation affect carbon fluxes?
It reduces the removal of atmospheric CO2 via photosynthesis
How does burning fossil fuels affect carbon fluxes?
It releases carbon dioxide into the atmosphere
How does increased numbers of livestock effect carbon fluxes?
They produce high levels of methane
What four trends of carbon flux are there?
Co2 levels fluctuate annually
Co2 levels conform to northern hemisphere patterns
Co2 levels are steadily increasing
Co2 levels are at their highest levels
Why do Co2 trends conform to northern hemisphere patterns?
As it contains more of the planets land mass
